Regenerative heat exchange apparatus

ABSTRACT

A regenerative heat exchange apparatus includes a heat storage tank, a heat storage material disposed inside the heat storage tank and having a heat storage capability and a heat rejection capability, a liquid passage covered by the heat storage material inside the heat storage tank, the liquid passage having a first straight pipe portion through which a liquid flows horizontally, a heat medium passage covered by the heat storage material inside the heat storage tank, the heat medium passage being adjacent to and in a set with the liquid passage, the heat medium passage having a second straight pipe portion through which a heat medium flows horizontally, the heat medium being at a temperature higher than the liquid. The first straight pipe portion is located vertically lower than the second straight pipe portion.

TECHNICAL FIELD

The present invention relates to a regenerative heat exchange apparatusthat includes a heat storage tank filled with a latent heat storagematerial, and a heat exchanger.

BACKGROUND ART

To bridge a temporal gap between demand and supply of heat energy,conventional heat exchange apparatuses employ heat storage materials inwhich heat can be temporarily stored for later use when the heat isneeded. Among such heat storage materials, a latent heat storagematerial, which utilizes latent heat produced during liquid-solid phasechange, is used due to its high heat storage density per volume. In thisregard, a solid phase of a heat storage material generally exhibits lowthermal conductivity. This means that when heat energy is transferred inand out of the heat storage material during storage and rejection ofheat, the solid phase acts as a thermal resistance to inhibit the entryand exit of heat. Further, a heat storage material undergoes a largevolume change when solidifying from a liquid phase to a solid phase.This causes the heat transfer surface to be exposed, leading todeteriorated heat exchange performance.

Accordingly, the regenerative heat exchange apparatus described inPatent Literature 1 employs the following configuration. A heat sourcethat covers the bottom surface of a heat storage tank, and a heat sourceplaced perpendicular to the bottom surface are provided to preventformation of air gaps within the heat storage tank. Further, convectionof the melted latent heat storage material is utilized to facilitatemelting of the remaining solid phase of the latent heat storagematerial.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 58-178191

SUMMARY OF INVENTION Technical Problem

With the regenerative heat exchange apparatus described in PatentLiterature 1, if the heat storage material within the heat storage tanksolidifies, to melt the solid phase of the heat storage material thatprecipitates around the heat exchanger, it is necessary to melt thesolid phase of the heat storage material within the entire heat storagetank. This increases the time required for heat storage. Further, withthis regenerative heat exchange apparatus, the rate of heat exchangedecreases as the solid phase grows. Consequently, if the regenerativeheat exchange apparatus is used under conditions where the required heatquantity increases or decreases, the volume of the heat exchange portionincreases, leading to increased size of the apparatus.

The present invention has been made to address the above-mentionedproblem, and accordingly it is an object of the present invention toprovide a regenerative heat exchange apparatus with which heat storagecan be performed in a short time, and when a solid phase of a heatstorage material precipitates on the heat transfer surface, the solidphase can be detached by melting by inputting heat for a short period oftime.

Solution to Problem

A regenerative heat exchange apparatus according to an embodiment of thepresent invention includes a heat storage tank, a heat storage materialdisposed inside the heat storage tank, the heat storage material havinga heat storage capability and a heat rejection capability, a liquidpassage covered by the heat storage material inside the heat storagetank, the liquid passage having a first straight pipe portion throughwhich a liquid flows horizontally, and a heat medium passage covered bythe heat storage material inside the heat storage tank, the heat mediumpassage being adjacent to and in a set with the liquid passage, the heatmedium passage having a second straight pipe portion through which aheat medium flows horizontally, the heat medium being at a temperaturehigher than the liquid. The first straight pipe portion is locatedvertically lower than the second straight pipe portion.

Advantageous Effects of Invention

With the regenerative heat exchange apparatus according to an embodimentof the present invention, a liquid passage and a heat medium passage aredisposed adjacent to each other, and a first straight pipe portion,which is a portion inside the liquid passage where a liquid flowshorizontally, is located vertically lower than a second straight pipeportion of the heat medium passage that is in a set with the firststraight pipe portion. Consequently, a solid phase that has precipitatedaround the liquid passage can be quickly melted away by the heat mediumsupplied to the heat medium passage. As a result, when the required heatquantity increases, heat output can be increased through direct heatexchange between the liquid and the heat medium.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram exemplarily illustrating an internal structure of aregenerative heat exchange apparatus according to Embodiment 1 of thepresent invention.

FIG. 2 is a cross-sectional view of a liquid passage and a heat mediumpassage that are disposed inside a heat storage tank of the regenerativeheat exchange apparatus according to Embodiment 1 of the presentinvention.

FIG. 3 is a schematic view illustrating melting and detachment of asolid phase of a heat storage material that has precipitated around aliquid passage of the regenerative heat exchange apparatus according toEmbodiment 1 of the present invention.

FIG. 4 is an enlarged view of the portion A illustrated in FIG. 1.

FIG. 5 is a cross-sectional view taken along arrow lines B-B illustratedin

FIG. 4.

FIG. 6 is an explanatory view of a regenerative heat exchange apparatusaccording to Embodiment 1 of the present invention, with sets of firstand second straight pipe portions being disposed in a staggeredarrangement.

FIG. 7 is a schematic view illustrating a fluid circuit that employs theregenerative heat exchange apparatus according to Embodiment 1 of thepresent invention.

FIG. 8 is a cross-sectional view of a liquid passage, a heat mediumpassage, and a heat-storage-material-solid-phase dividing plate of aregenerative heat exchange apparatus according to Embodiment 2 of thepresent invention.

FIG. 9 is a cross-sectional view of a liquid passage, a heat mediumpassage, and a heater of a regenerative heat exchange apparatusaccording to Embodiment 3 of the present invention.

FIG. 10 is a cross-sectional view of a regenerative heat exchangeapparatus according to Embodiment 4 of the present invention,illustrating the relationship between a liquid passage, a heat mediumpassage, and a heat-storage-material-solid-phase dividing plate.

FIG. 11 is a cross-sectional view of a regenerative heat exchangeapparatus according to Embodiment 5 of the present invention,illustrating the relationship between a liquid passage, a heat mediumpassage, and a heat-storage-material-solid-phase dividing plate.

FIG. 12 is a cross-sectional view taken along arrow lines C-Cillustrated in FIG. 11.

DESCRIPTION OF EMBODIMENTS Embodiment 1

Regenerative heat exchange apparatuses according to embodiments of thepresent invention will be described below with reference to thedrawings. In the following description of the embodiments, a structure,a material, or other features described with reference to a givenembodiment may be, for example, replaced with or added to a structure, amaterial, or other features described with reference to anotherembodiment as long as no technical inconsistency arises as a result.

FIG. 1 is a diagram exemplarily illustrating an internal structure of aregenerative heat exchange apparatus according to Embodiment 1 of thepresent invention. FIG. 2 is a cross-sectional view of a liquid passageand a heat medium passage that are disposed inside a heat storage tankof the regenerative heat exchange apparatus according to Embodiment 1 ofthe present invention. In one example, the regenerative heat exchangeapparatus according to Embodiment 1 illustrated in FIGS. 1 and 2 employsa coil-tank heat exchange system. The regenerative heat exchangeapparatus includes a heat storage tank 1, a heat storage material 2charged into the heat storage tank 1, a liquid passage 3 that obtainsheat from the heat storage material 2, a heat medium passage 4 thatprovides heat to the heat storage material 2, aheat-storage-material-solid-phase dividing plate 5 positioned to crossthe liquid passage 3 and the heat medium passage 4, and a temperaturesensor 6 located beside the outlet where the liquid passage 3 leaves theheat storage tank 1. The regenerative heat exchange apparatus accordingto Embodiment 1 further includes a flow rate control unit 9 thatcontrols the flow rate of a liquid through the liquid passage 3 and theflow rate of a heat medium through the heat medium passage 4.

The heat storage tank 1 contains the heat storage material 2, the liquidpassage 3, and the heat medium passage 4. The heat storage tank 1 ismade of a material that is resistant to corrosion by the heat storagematerial 2, such as stainless, iron, or a nickel chrome alloy.

The heat storage material 2 is a latent heat storage material whosemelting point lies within the range of temperatures used. Unlike asensible heat storage material that stores only sensible heat, such aswater, a latent heat storage material is also able to store the heat offusion, which is latent heat, and thus has a high heat storage densityper unit volume. Accordingly, use of a latent heat storage materialhelps reduce the size of the heat storage tank 1 in comparison to use ofa sensible heat storage material. As the heat storage material 2 changesin phase from solid to liquid when heated by the heat medium, the heatstorage material 2 stores latent heat (the heat of fusion). Upon passageof a liquid used to receive heat, the heat storage material 2 has itsheat taken away and solidifies from a liquid to a solid, rejecting heat.

As for specific examples of the heat storage material 2, examples ofsaturated hydrocarbon-based materials include straight-chain paraffinsuch as decane, undecane, dodecane, tridecane, tetradecane, pentadecane,hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane,docosan, tricosane, tetracosane, pentacosane, hexacosane, heptacosane,octacosane, nonacosane, triacontane, hentriacontane, dotriacontane,tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane,heptatriacontane, octatriacontane, nonatriacontane, tetracontane,dotetracontane, tritetracontane, tetratetra tetracontane,hexatetracontane, octatetracontane, pentacontane, hexacontane,heptacontane, and hectane. Examples of fatty acid-based materialsinclude palmitic acid, stearic acid, myristic acid, oleic acid,palmitoleic acid, y-linolenic acid, linoleic acid, arachidonic acid,α-linolenic acid, decanoic acid, pentadecanoic acid, heptadecanoic acid,behenic acid, lignoceric acid, decenoic acid, pentadecenoic acid, andmyristoleic acid. Examples of metal-based materials include mercury,potassium, sodium, gallium, indium, bismuth, aluminum, zinc, silicon,magnesium, copper, tin, lead, cadmium, and an alloy including at leastone of the above metals. Examples of sugar alcohol-based materialsinclude D-threitol, L-threitol, DL-threitol, meso-erythritol,L-erythritol, D-erythritol, DL-erythritol, pentaerythritol,dipentaerythritol, xylitol, D-arabitol, L-arabitol, DL-arabitol,D-sorbitol, L-sorbitol, DL-sorbitol, D-mannitol, L-mannitol, andDL-mannitol. Examples of hydrated salt-based materials include potassiumfluoride tetrahydrate, potassium chloride hexahydrate, lithium nitratetrihydrate, sodium acetate trihydrate, sodium thiosulfate pentahydrate,sodium sulfate decahydrate, disodium hydrogen phosphate, Iron chloridehexahydrate, magnesium sulfate heptahydrate, lithium acetate dihydrate,sodium hydroxide monohydrate, barium hydroxide octahydrate, strontiumhydroxide octahydrate, aluminum ammonium sulfate hexahydrate, andaluminum potassium sulfate hexahydrate. Examples of molten salt-basedmaterials include aluminum chloride, lithium nitrate, sodium nitrate,potassium nitrate, lithium hydroxide, potassium chloride, lithiumchloride, magnesium chloride, potassium chloride, potassium fluoride,lithium fluoride, lithium carbonate, potassium carbonate, bariumnitrate, and sodium carbonate. Other example materials include clathratehydrates such as tetrabutylammonium bromide, and water. Other than thosementioned above, any material can be used as long as the material has amelting point within the range of temperatures used and undergoesliquid-solid phase change.

The liquid passage 3 is a passage covered by the heat storage material2, and receives heat from the heat storage material 2. The liquidpassage 3 has a first straight pipe portion 3 a through which a liquidflows horizontally. As the material of the liquid passage 3, forexample, a metal such as copper, aluminum, stainless, titanium, or anickel chrome alloy, or a resin such as polypropylene, polyethyleneterephthalate, polyethylene, or polycarbonate is used. The liquidpassage 3 used is in the form of, for example, a circular pipe, amulti-hole pipe, a flat pipe, or a twisted pipe. A pipe with an insidediameter of 1 to 20 mm and a pipe wall thickness of 0.3 to 2.0 mm ispreferably used as the liquid passage 3. As the liquid that flowsthrough the liquid passage 3, water, silicone oil, or brine such asethylene glycol or propylene glycol is used.

The heat medium passage 4 is covered by the heat storage material 2, andprovides heat to the heat storage material 2. The heat medium passage 4,which is adjacent to and disposed side by side with (hereinafterreferred to as “in a set with” the liquid passage 3, has a secondstraight pipe portion 4 a through which a heat medium flowshorizontally. As the material of the heat medium passage 4, a metal suchas copper, aluminum, stainless, titanium, or a nickel chrome alloy, or aresin such as polypropylene, polyethylene terephthalate, polyethylene,or polycarbonate is used. The heat medium passage 4 used is in the formof, for example, a circular pipe, a multi-hole pipe, a flat pipe, or atwisted pipe. A pipe with an inside diameter of 1 to 20 mm and a pipewall thickness of 0.3 to 2.0 mm is preferably used as the heat mediumpassage 4. Examples of the liquid that flows through the heat mediumpassage 4 include water, silicone oil, or brine such as ethylene glycolor propylene glycol.

As illustrated in FIG. 1, the first straight pipe portion 3 a of theliquid passage 3 and the second straight pipe portion 4 a of the heatmedium passage 4 are disposed in a set and arranged in multiple stages(six stages in FIG. 1) in the up-down direction, with the first straightpipe portion 3 a being located vertically lower than the second straightpipe portion 4 a. The second straight pipe portions 4 a of the heatmedium passage 4 that are adjacent in the up-down direction areconnected at their one end, resulting in a configuration such that theheat medium passage 4 meanders in the up-down direction. Likewise, thefirst straight pipe portions 3 a of the liquid passage 3 that areadjacent in the up-down direction are connected at their one end,resulting in a configuration that the liquid passage 3 meanders in theup-down direction.

The heat-storage-material-solid-phase dividing plate 5 has athrough-hole 5 c that is penetrated by the liquid passage 3 and the heatmedium passage 4. The heat-storage-material-solid-phase dividing plate 5is positioned to cross the outer periphery of each of the liquid passage3 and the heat medium passage 4. The heat-storage-material-solid-phasedividing plate 5 is used for the following purpose: when heat is takenaway from the heat storage material 2 by the liquid passage 3 and thesolid phase of the heat storage material 2 precipitates, theheat-storage-material-solid-phase ividing plate 5 transfers the heatfrom the heat medium to the heat storage material 2 to divide the solidphase in a direction that crosses the liquid passage 3. Theheat-storage-material-solid-phase dividing plate 5 is preferably made ofa material with high thermal conductivity, for example, copper,aluminum, stainless, titanium, or a nickel chrome alloy. As theheat-storage-material-solid-phase dividing plate 5, a plate with athickness of, for example, 0.3 to 2 mm is preferably used.

The temperature sensor 6 detects the outlet temperature of the liquidpassage 3. In a heat rejection process, if a solid phase of the heatstorage material 2 precipitates on the outer periphery of the liquidpassage 3, the solid phase acts as a thermal resistance and impedes arise in liquid temperature. If the liquid supply is continued in thisstate, the liquid temperature at the outlet does not rise to a desiredtemperature. Accordingly, it is necessary to detect the liquidtemperature at the outlet, and supply the heat medium to the heat mediumpassage 4 when the liquid temperature at the outlet has become less thanor equal to a predetermined temperature. It is desired that the flowrate control unit 9 be able to control the rate of supply of the heatmedium based on the temperature detected by the temperature sensor 6.The supply of the heat medium to the heat medium passage 4 is stoppedonce the liquid temperature at the outlet has become greater than orequal to the predetermined temperature. In this regard, by furtherdetecting the outlet temperature of the heat medium passage 4 at thistime, it is possible to stop the supply of the heat medium when thetemperature of the heat medium has become greater than or equal to apredetermined temperature, even when liquid supply to the liquid passage3 is being stopped.

The following describes each step of storage and rejection of heat intothe heat storage material 2 in the regenerative heat exchange apparatusaccording to Embodiment 1. When the regenerative heat exchange apparatusis at a temperature less than or equal to the melting point of the heatstorage material 2, the heat storage material 2 is present in solidstate within the heat storage tank 1.

In a heat storage process, the heat medium is supplied to the heatmedium passage 4, and heat is given to the heat storage material 2through heat exchange between the heat storage material 2 and the heatmedium. The heat storage material 2 gradually rises in temperature, andbegins to melt once its temperature has reached a temperature greaterthan or equal to the melting point. The heat storage process is regardedcomplete when the heat storage material 2 has completely melted andalmost no temperature difference is observed and hence no heat exchangeis performed between the heat medium and the heat storage material 2.

In a heat rejection process, as the liquid is supplied to the liquidpassage 3, the heat storage material 2 and the liquid exchange heat, andthe liquid obtains heat from the heat storage material 2. The heatstorage material 2 gradually drops in temperature, and begins tosolidify once its temperature has reached a temperature less than orequal to the melting point. Once solidified, the heat storage material 2acts as a thermal resistance. This thermal resistance increases withincreasing thickness of the solid phase, leading to reduced rate of heatexchange.

A heat storage-heat rejection process refers to a process thatsimultaneously performs the required heat storage and heat rejectionwhen the liquid temperature at the outlet of the heat storage tank 1 hasbecome less than or equal to a target temperature. To prevent the liquidtemperature from becoming less than or equal to a required temperature,when the liquid temperature has reached a temperature less than or equalto a target temperature, the heat medium is supplied simultaneously withliquid supply. In this regard, by placing the liquid passage 3 and theheat medium passage 4 adjacent to each other, the liquid in the liquidpassage 3 obtains heat from the heat medium in addition to the heat fromthe heat storage material 2 in the surroundings, and consequently risesin temperature. The heat medium in the heat medium passage 4 gives heatto the liquid in the liquid passage 3, and at the same time, the heatmedium gives heat to the heat storage material 2 in the surroundings tothereby melt the solid phase of the heat storage material 2. In otherwords, the adjacent placement of the liquid passage 3 and the heatmedium passage 4 makes it possible to perform heat storage and heatrejection simultaneously.

Next, the exchange of heat between the liquid passage 3 and the heatmedium passage 4 will be described with reference to FIG. 3. FIG. 3schematically illustrates melting and detachment of a solid phase of theheat storage material that has precipitated around the liquid passage ofthe regenerative heat exchange apparatus according to Embodiment 1 ofthe present invention.

Step S1 shows a state in which, as the liquid is supplied to the liquidpassage 3, heat is taken away from the heat storage material 2 that ispresent in the vicinity of the outer periphery of the liquid passage 3,resulting in precipitation of a solid phase of the heat storage material2. In step S1, heat transfer from the liquid passage 3 causes aheat-storage-material solid phase 20 to precipitate also around the heatmedium passage 4. As the liquid is supplied, the heat-storage-materialsolid phase 20 increases in thickness, causing the liquid temperature atthe outlet of the heat storage tank 1 to gradually decrease.

Step S2 shows a state in which the heat medium is being supplied to theheat medium passage 4. In step S2, the heat medium supplied to the heatmedium passage 4 first gives heat to the heat-storage-material solidphase 20 present around the heat medium passage 4. Theheat-storage-material solid phase 20 thus begins to melt.

Step S3 shows a state in which the supply of the heat medium to the heatmedium passage 4 is further continued from the state of step S2. In stepS3, the heat-storage-material solid phase 20 around the heat mediumpassage 4 has completely melted with the heat given from the heatmedium, and the heat-storage-material solid phase 20 around the liquidpassage 3 beings to melt.

Step S4 shows a state in which the supply of the heat medium to the heatmedium passage 4 is further continued from the state of step S3. In stepS4, the heat-storage-material solid phase 20 around the area of theliquid passage 3 near the heat medium passage 4 melts, and the remainingheat-storage-material solid phase 20 around the liquid passage 3detaches from the liquid passage 3. This causes the surface of theliquid passage 3 to be exposed, leading to increased heat exchangecapacity.

In this regard, if the heat storage material 2 has a higher density insolid state than in liquid state, melting the vertically upper portionof the liquid passage 3 causes the heat-storage-material solid phase 20to be stripped off vertically downward due to the difference in specificgravity. Consequently, the surface of the liquid passage 3 can bequickly exposed, thus quickly increasing the heat exchange capacity.This configuration helps prevent the liquid temperature at the outlet ofthe heat storage tank 1 from decreasing to a temperature less than orequal to a target temperature, thus avoiding stopping of liquid supply.By contrast, if the heat storage material 2 is, for example, water, theheat storage material 2 has a lower density in solid state than inliquid state. Accordingly, to quickly strip the solid (ice) off theliquid passage 3, the heat medium passage 4 needs to be disposed underthe liquid passage 3.

FIG. 4 is an enlarged view of the portion A illustrated in FIG. 1. FIG.5 is a cross-sectional view taken along arrow lines B-B illustrated inFIG. 4. If the end portions of the heat medium passage 4 and the liquidpassage 3 arranged in a set are bent in an U-shape as illustrated inFIG. 4, bending the U-shaped portion obliquely relative to the verticaldirection as illustrated in FIG. 5 ensures that the positionalrelationship between the set of the heat medium passage 4 and the liquidpassage 3 relative to the vertical direction can be maintained also fortheir end portion. In other words, the connecting part of two secondstraight pipe portions 4 a that are adjacent in the up-down direction islocated vertically higher than the connecting part of two first straightpipe portions 3 a that are adjacent in the up-down direction. At thistime, as illustrated in FIG. 5, interference between passages can beavoided by ensuring that the following relationship be satisfied:(r1+r2+d)sinθ≥r1+r2, where r1 is the radius of the heat medium passage4, r2 is the radius of the liquid passage 3, d is the distance betweenthe outer periphery of the first straight pipe portion 3 a of the liquidpassage 3 and the outer periphery of the second straight pipe portion 4a of the heat medium passage 4 that is in a set with the liquid passage3, and θ is the bend angle relative to the vertical direction.

If the first straight pipe portion 3 a and the second straight pipeportion 4 a are disposed in a set and arranged in multiple stages in theup-down direction as illustrated in FIG. 1, the second straight pipeportion 4 a in a given set is disposed such that its distance “d” fromthe first straight pipe portion 3 a being in a set with the secondstraight pipe portion 4 a is less than its distance “D” from the firststraight pipe portion 3 a in another set (d<D) as illustrated in FIG. 5.This configuration ensures that the heat from a given second straightpipe portion 4 a is transferred preferentially to the first straightpipe portion 3 a that is in a set with the second straight pipe portion4 a.

FIG. 6 is an explanatory view of a regenerative heat exchange apparatusaccording to Embodiment 1 of the present invention, with sets of firstand second straight pipe portions disposed in a staggered arrangement.As illustrated in FIG. 6, if the sets of the first straight pipe portion3 a and the second straight pipe portion 4 a are disposed in a staggeredarrangement as viewed in vertical cross-section of the heat storage tank1, the heat-storage-material solid phase 20 is readily allowed tosediment toward the vertically lower portion of the heat storage tank 1when stripped off. This helps increase the heat exchange capacity.

Further, the diameter of the second straight pipe portion 4 a of theheat medium passage 4 is made smaller than the diameter of the firststraight pipe portion 3 a of the liquid passage 3. This helps reduce theprecipitation of the heat-storage-material solid phase 20 around theheat medium passage 4, thus reducing the time required to melt theheat-storage-material solid phase 20. As a result, the heat exchangecapacity can be increased quickly.

If the number of heat medium passages 4, which are in a set with theliquid passages 3, is greater than the number of liquid passages 3, thetime required to melt the heat-storage-material solid phase 20 with theheat from the heat medium passages 4 is reduced, leading to enhancedheat exchange performance.

Although FIG. 1 illustrates a coil-tank heat exchange system as anexemplary regenerative heat exchange apparatus according to Embodiment1, the similar effects as those mentioned above can be obtained alsowith shell-and-tube, double-pipe, and plate-fin heat exchange systems.In melting the heat-storage-material solid phase 20 by the heat medium,if the heat-storage-material solid phase 20 is attached over a longlength at this time, such a melted heat-storage-material solid phase 20does not detach quickly. The regenerative heat exchange apparatusaccording to Embodiment 1 addresses this problem as follows. That is, toensure that the heat-storage-material solid phase 20 does not form overa long length along the liquid passage 3, theheat-storage-material-solid-phase dividing plate 5 is disposed to crossthe liquid passage 3 and the heat medium passage 4. Theheat-storage-material-solid-phase dividing plate 5 is used to divide theheat-storage-material solid phase 20 that has precipitated around theliquid passage 3, in a direction that crosses the liquid passage 3 bythe heat transferred from the heat medium flowing in the heat mediumpassage 4. The divided heat-storage-material solid phase 20 is quicklystripped off the liquid passage 3, leaving the heat transfer surface ofthe liquid passage 3 exposed. This makes it possible to quickly increasethe heat exchange capacity.

Next, the temperature sensor 6 used to control storage and rejection ofheat will be described with reference to FIG. 7. FIG. 7 schematicallyillustrates a fluid circuit that employs the regenerative heat exchangeapparatus according to Embodiment 1 of the present invention. In theheat rejection process, as a liquid is supplied to the liquid passage 3and heat is taken away from the heat storage material 2 by the liquid,the heat-storage-material solid phase 20 precipitates around the surfaceof the liquid passage 3. The heat-storage-material solid phase 20 actsas a thermal resistance due to its low thermal conductivity.Consequently, the heat given to the liquid from the heat storagematerial 2 decreases. As the liquid supply is further continued, theliquid temperature at the outlet of the heat storage tank 1 eventuallyreaches a temperature less than or equal to a desired temperature,causing the liquid supply to be stopped. Accordingly, as illustrated inFIG. 7, the flow rate control unit 9 performs the following heatstorage-heat rejection process. That is, the temperature of the liquidpassage 3 at the outlet of the heat storage tank 1 is detected by thetemperature sensor 6, and the heat medium is supplied from a heat source7 to the heat medium passage 4 if the detected temperature has becomeless than or equal to a target temperature. Because the rate of heatrejection is determined by the thickness of the heat-storage-materialsolid phase 20, whether the heat-storage-material solid phase 20 hasbeen stripped off can be determined by calculation from the liquidoutlet temperature. Accordingly, the heat rejection process is regardedcomplete when the liquid outlet temperature detected by the temperaturesensor 6 has become greater than or equal to a target temperature.

Now, a case is considered where liquid supply is stopped in the middleof the heat storage-heat rejection process, and then a transition to theheat storage process is made. In this case, it is not possible toidentify the time of completion of the heat rejection process from theoutlet temperature of the liquid passage 3. Accordingly, with theregenerative heat exchange apparatus, the temperature sensor 6 is alsodisposed in the same manner at the outlet where the heat medium passage4 leaves the heat storage tank 1, and the heat storage process isregarded complete when the outlet temperature of the heat medium hasbecome greater than or equal to a predetermined temperature.

As described above, with the regenerative heat exchange apparatusaccording to Embodiment 1, the liquid passage 3 and the heat mediumpassage 4 are disposed adjacent to each other, and the first straightpipe portion 3 a where the liquid flows horizontally inside the liquidpassage 3 is located vertically lower than the second straight pipeportion 4 a of the heat medium passage 4 that is in a set with the firststraight pipe portion 3 a. Consequently, a solid phase that hasprecipitated around the liquid passage 3 can be quickly melted away bymeans of the heat medium supplied to the heat medium passage 4. As aresult, when the required heat quantity increases, heat output can bequickly increased through direct heat exchange between the liquid andthe heat medium.

With the regenerative heat exchange apparatus according to Embodiment 1,the flow rate control unit 9 controls the flow rate of the liquidthrough the liquid passage 3 and the flow rate of the heat mediumthrough the heat medium passage 4 based on at least one of a liquidtemperature and a heat medium temperature that have been detected by thetemperature sensor 6. Consequently, the upper portion of theheat-storage-material solid phase 20 that has precipitated around theliquid passage 3 can be melted in preference to other portions. Thisenables quick detachment of the lower portion of theheat-storage-material solid phase 20 with a comparatively large specificgravity that has remained un-melted. As a result, the heat transfersurface of the liquid passage 3 can be exposed to thereby quicklyincrease the rate of heat exchange.

Embodiment 2

Next, a regenerative heat exchange apparatus according to Embodiment 2of the present invention will be described with reference to FIG. 8.FIG. 8 is a cross-sectional view of a liquid passage, a heat mediumpassage, and a heat-storage-material-solid-phase dividing plate of theregenerative heat exchange apparatus according to Embodiment 2 of thepresent invention. A description of components identical to those of theregenerative heat exchange apparatus according to Embodiment 1 will beomitted as appropriate.

With the regenerative heat exchange apparatus according to Embodiment 2,the heat-storage-material-solid-phase dividing plate 5 has a shape suchthat the heat-storage-material-solid-phase dividing plate 5 crosses theliquid passage 3 and the heat medium passage 4. Theheat-storage-material-solid-phase dividing plate 5 has a second covering5 b that covers the outer peripheral surface of the heat medium passage4, and a first covering 5 a that covers the outer peripheral surface ofthe liquid passage 3. With the regenerative heat exchange apparatusaccording to Embodiment 2, the heat-storage-material-solid-phasedividing plate 5 is positioned to cross the liquid passage 3 and theheat medium passage 4. This helps reduce diffusion of heat from the heatmedium passage 4 to a liquid phase of the heat storage material in thesurroundings. As a result, in the heat storage process and the heatstorage-heat rejection process, the heat-storage-material solid phase 20can be melted efficiently, and stripped off the liquid passage 3. Thatis, the regenerative heat exchange apparatus according to Embodiment 2reduces the time taken for the heat-storage-material solid phase 20 tobe divided in a direction that crosses the liquid passage 3. This helpsavoid situations where, as liquid supply is continued, the liquidtemperature at the outlet of the heat storage tank 1 becomes less thanor equal to a desired temperature and the liquid supply consequentlystops.

Further, the heat-storage-material-solid-phase dividing plate 5 isshaped such that the length of the liquid passage 3 in the radialdirection is greater than the length of the heat medium passage 4 in theradial direction. Specifically, the heat-storage-material-solid-phasedividing plate 5 is formed in a shape such that the average distancebetween the outer peripheral surface of the liquid passage 3 and theinner peripheral surface of the first covering 5 a is greater than theaverage distance between the outer peripheral surface of the heat mediumpassage 4 and the inner peripheral surface of the second covering 5 b.

The above-mentioned shape of the heat-storage-material-solid-phasedividing plate 5 ensures that, in the heat storage process and the heatstorage-heat rejection process, the heat of the heat medium supplied tothe heat medium passage 4 is efficiently transferred to theheat-storage-material solid phase 20 that has precipitated around theliquid passage 3. This reduces the time taken for theheat-storage-material solid phase 20 to be divided in a direction thatcrosses the liquid passage 3. Consequently, the heat storage process andthe heat storage-heat rejection process are reduced in duration, whichhelps avoid stopping of liquid supply. In this regard, as the shape ofthe heat-storage-material-solid-phase dividing plate 5 resembles thecross-sectional shape of the heat-storage-material solid phase 20 thatprecipitates around the liquid passage 3 and the heat medium passage 4,transfer of heat from the heat medium to the heat-storage-material solidphase 20 becomes more efficient.

The heat-storage-material solid phase 20 is greater in density than theliquid phase of the heat storage material. Consequently, the thicknessof the solid phase of the heat storage material 2 is greater in a regionbelow the central portion of the liquid passage 3 than in a region abovethe central portion. Accordingly, the shape of theheat-storage-material-solid-phase dividing plate 5 is such that itsinside diameter is greater in a region corresponding to the lowerportion of the liquid passage 3 than in a region corresponding to theupper portion of the liquid passage 3. The heat-storage-material solidphase 20 that precipitates around the heat medium passage 4 has agreater thickness on the side facing the liquid passage 3. Accordingly,the inside diameter of the heat-storage-material solid phase 20 isgreater in a region below the center of the heat medium passage 4 thanin a region above the center.

Accordingly, the heat-storage-material-solid-phase dividing plate 5 isformed in a shape such that the average distance between the outerperipheral surface of the heat medium passage 4 and the inner peripheralsurface of the second covering 5 b in a region vertically lower than thesecond straight pipe portion 4 a is less than the average distancebetween the outer peripheral surface of the liquid passage 3 and theinner peripheral surface of the first covering 5 a in a regionvertically lower than the first straight pipe portion 3 a. Theabove-mentioned configuration of the regenerative heat exchangeapparatus according to Embodiment 2 helps efficiently transfer heat fromthe heat medium passage 4 to the liquid passage 3, thus reducing thetime required to melt and detach the heat-storage-material solid phase20 that has precipitated around the liquid passage 3. This enables aquick increase in heat exchange capacity.

Embodiment 3

Next, a regenerative heat exchange apparatus according to Embodiment 3of the present invention will be described with reference to FIG. 9.FIG. 9 is a cross-sectional view of a liquid passage, a heat mediumpassage, and a heater of the regenerative heat exchange apparatusaccording to Embodiment 3 of the present invention. A description ofcomponents identical to those of the regenerative heat exchangeapparatus according to Embodiments 1 and 2 will be omitted asappropriate.

As illustrated in FIG. 9, the regenerative heat exchange apparatusaccording to Embodiment 3 includes a heater 8 located vertically abovethe liquid passage 3. With the regenerative heat exchange apparatusaccording to Embodiment 3, if a situation arises where the heat from theheat medium passage 4 alone is not sufficient to bring the liquid to atemperature higher than or equal to a target temperature, the heater 8can be energized to supplement the heat shortage. In addition toavoiding stopping of liquid supply, this configuration makes it possibleto melt the heat storage material 2 precipitating around the liquidpassage 3. As a result, the heat exchange capacity of the regenerativeheat exchange apparatus can be quickly increased. As for theenergization of the heater 8, consumption of unnecessarily largeelectric power by the heater 8 can be minimized by detecting the outlettemperature of the liquid passage 3 by the temperature sensor 6 andcontrolling the flow rate by the flow rate control unit 9.

Embodiment 4

Next, a regenerative heat exchange apparatus according to Embodiment 4of the present invention will be described with reference to FIG. 10.FIG. 10 is a cross-sectional view of the regenerative heat exchangeapparatus according to

Embodiment 4 of the present invention, illustrating the relationshipbetween a liquid passage, a heat medium passage, and aheat-storage-material-solid-phase dividing plate. A description ofcomponents identical to those of the regenerative heat exchangeapparatus according to Embodiments 1 to 3 will be omitted asappropriate.

As illustrated in FIG. 10, the regenerative heat exchange apparatusaccording to Embodiment 4 includes a slit 10 located vertically abovethe heat medium passage 4 within the plane of theheat-storage-material-solid-phase dividing plate 5. With theregenerative heat exchange apparatus according to Embodiment 4, thepresence of the slit 10 reduces the transmission of heat to a regionlocated vertically above the heat medium passage 4. Heat from the heatmedium passage 4 can be thus efficiently transferred to the liquidpassage 3 to reduce the time required to melt and detach theheat-storage-material solid phase 20 that has precipitated around theliquid passage 3. This makes it possible to quickly increase the heatexchange capacity.

Although not illustrated in detail in FIG. 10, if the regenerative heatexchange apparatus according to Embodiment 4 is further provided withslits positioned to the left and right of the heat medium passage 4,heat from the heat medium passage 4 can be efficiently transferred tothe liquid passage 3 to further reduce the time required to melt anddetach the heat-storage-material solid phase 20 that has precipitatedaround the liquid passage 3, thus making it possible to quickly increasethe heat exchange capacity.

Embodiment 5

Next, a regenerative heat exchange apparatus according to Embodiment 5of the present invention will be described with reference to FIGS. 11and 12. FIG. 11 is a cross-sectional view of the regenerative heatexchange apparatus according to Embodiment 5 of the present invention,illustrating the relationship between a liquid passage, a heat mediumpassage, and a heat-storage-material-solid-phase dividing plate. FIG. 12is a cross-sectional view taken along arrow lines C-C illustrated inFIG. 11. A description of components identical to those of theregenerative heat exchange apparatus according to Embodiments 1 to 3will be omitted as appropriate.

As illustrated in FIGS. 11 and 12, the regenerative heat exchangeapparatus according to Embodiment 5 includes a cut-and-raised portion 11located vertically above the heat medium passage 4 within the plane ofthe heat-storage-material-solid-phase dividing plate 5. Thecut-and-raised portion 11 is formed by cutting and raising a part of theheat-storage-material-solid-phase dividing plate 5 forward. Thecut-and-raised portion 11 is formed by cutting and raising such that thecut in the cut area is located vertically lower than a part of thecut-and-raised portion 11 that is left uncut. With the regenerative heatexchange apparatus according to Embodiment 5, when heat given from theheat medium passage 4 is transferred to the liquid passage 3 via theheat-storage-material-solid-phase dividing plate 5, the presence of thecut-and-raised portion 11 minimizes transmission of heat in thevertically upward direction. This configuration of the regenerative heatexchange apparatus according to Embodiment 5 helps efficiently transferheat from the heat medium passage 4 to the liquid passage 3, thusreducing the time required to melt and detach the heat-storage-materialsolid phase 20 that has precipitated around the liquid passage 3. As aresult, the heat exchange capacity can be increased quickly.

Further, with the regenerative heat exchange apparatus according toEmbodiment 5, the cut-and-raised portion 11 is formed by cutting andraising such that the cut in the cut area is located vertically lowerthan a part of the cut-and-raised portion 11 that is left uncut.Consequently, heat can be transferred from the heat medium passage 4 tothe liquid passage 3 with further enhanced efficiency to thereby furtherreduce the time required to detach by melting the heat-storage-materialsolid phase 20 that has precipitated around the liquid passage 3. Thismakes it possible to quickly increase the heat exchange capacity. Theconfiguration of the cut-and-raised portion 11 in FIGS. 11 and 12 isillustrative of one example and should not be construed as beinglimiting. The cut-and-raised portion 11 is formed in variousconfigurations that depend on the actual implementation conditions.

REFERENCE SIGNS LIST

1 heat storage tank 2 heat storage material 3 liquid passage 3 a firststraight pipe portion 4 heat medium passage 4 a second straight pipeportion heat-storage-material-solid-phase dividing plate 5 a firstcovering 5 b second covering 5 c through-hole 6 temperature sensor 7heat source 8 heater 9 flow rate control unit 10 slit 11 cut-and-raisedportion 20 heat-storage-material solid phase

1. A regenerative heat exchange apparatus comprising: a heat storagetank; a heat storage material disposed inside the heat storage tank, theheat storage material having a heat storage capability and a heatrejection capability; a liquid passage covered by the heat storagematerial inside the heat storage tank, the liquid passage having a firststraight pipe portion through which a liquid flows horizontally; and aheat medium passage covered by the heat storage material inside the heatstorage tank, the heat medium passage being adjacent to and in a setwith the liquid passage, the heat medium passage having a secondstraight pipe portion through which a heat medium flows horizontally,the heat medium being at a temperature higher than the liquid, whereinthe first straight pipe portion is located vertically lower than thesecond straight pipe portion.
 2. The regenerative heat exchangeapparatus of claim 1, wherein the second straight pipe portion has apipe diameter less than a pipe diameter of the first straight pipeportion.
 3. The regenerative heat exchange apparatus of claim 1, whereinthe heat medium passage comprises heat medium passages in a numbergreater than the number of the liquid passages.
 4. The regenerative heatexchange apparatus of claim 1, wherein the first straight pipe portionand the second straight pipe portion are disposed in a set and arrangedin multiple stages in an up-down direction, wherein the second straightpipe portions of the heat medium passage that are adjacent in theup-down direction are connected at their one end such that the heatmedium passage meanders in the up-down direction, and wherein the firststraight pipe portions of the liquid passage that are adjacent in theup-down direction are connected at their one end such that the liquidpassage meanders in the up-down direction.
 5. The regenerative heatexchange apparatus of claim 4, wherein a mean distance between the firststraight pipe portion and the second straight pipe portion disposed in aset and arranged in multiple stages in the up-down direction is lessthan a distance between the second straight pipe portion in one stageand the first straight pipe portion in another stage adjacent to the onestage.
 6. The regenerative heat exchange apparatus of claim 4, wherein,when viewed in vertical cross-section of the heat storage tank, thefirst straight pipe portion and the second straight pipe portiondisposed in a set and arranged in multiple stages in the up-downdirection are disposed in a staggered arrangement.
 7. The regenerativeheat exchange apparatus of claim 4, wherein a connecting part of thesecond straight pipe portions that are adjacent in the up-down directionis located vertically higher than a connecting part of the firststraight pipe portions that are adjacent in the up-down direction. 8.The regenerative heat exchange apparatus of claim 1, further comprising:a temperature sensor configured to detect at least one of a liquidtemperature and a heat medium temperature, the liquid temperature beinga temperature of the liquid flowing through the liquid passage, the heatmedium temperature being a temperature of the heat medium flowingthrough the heat medium passage; and a flow rate control unit configuredto, based on a temperature detected by the temperature sensor, control aflow rate of the liquid through the liquid passage and a flow rate ofthe heat medium through the heat medium passage.
 9. The regenerativeheat exchange apparatus of claim 1, further comprising a dividing platepositioned to cross the liquid passage and the heat medium passage. 10.The regenerative heat exchange apparatus of claim 9, wherein the liquidpassage and the heat medium passage each have a tubular configuration,wherein the dividing plate includes a first covering to cover an outerperipheral surface of the liquid passage, a second covering to cover anouter peripheral surface of the heat medium passage, and wherein anaverage distance between the outer peripheral surface of the liquidpassage and an inner peripheral surface of the first covering is greaterthan an average distance between the outer peripheral surface of theheat medium passage and an inner peripheral surface of the secondcovering.
 11. The regenerative heat exchange apparatus of claim 10,wherein the dividing plate has a shape such that an average distancebetween an outer peripheral surface of the heat medium passage and theinner peripheral surface of the second covering in a region verticallylower than the second straight pipe portion is less than an averagedistance between an outer peripheral surface of the liquid passage andthe inner peripheral surface of the first covering in a regionvertically lower than the first straight pipe portion.
 12. Theregenerative heat exchange apparatus of claim 9, wherein the dividingplate includes a slit located vertically above the second straight pipeportion.
 13. The regenerative heat exchange apparatus of claim 9,wherein the dividing plate includes a cut-and-raised portion, thecut-and-raised portion being formed by cutting and raising a part of thedividing plate located vertically above the second straight pipeportion.
 14. The regenerative heat exchange apparatus of claim 13,wherein the cut-and-raised portion is formed by cutting and raising suchthat a cut in a cut area of the cut-and-raised portion is locatedvertically lower than a part of the cut-and-raised portion that is leftuncut.
 15. The regenerative heat exchange apparatus of claim 1, furthercomprising a heater located vertically above and adjacent to the liquidpassage to provide heat to the liquid passage.